Respirometric balance and analysis of four microalgae
Sydney, Eduardo Bittencourt
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Abstract: As a consequence of global warming many technologies are being developed in order to remove carbon dioxide from air. Biological carbon fixation through microalgae cultivation seems to be the most interesting one, since they allow the use of residual waters as media for growth, and industrial gases as carbon sources. Growth kinetics, metabolic behavior, nutrient requirement, biomass composition and carbon fixation capacity are essential data for industrial processes development. Such data were evaluated in four microalga of industrial interest cultivated in artificial medium with CO2 as carbon source: Spirulina platensis, Dunaliella tertiolecta, Chlorella vulgaris and Botryococcus braunii. A respirometric balance based on gases analysis was used to evaluate carbon dioxide fixation rate and ion chromatography was employed to determine rate of consumption of nitrogen, phosphorus, potassium and ma nesium for each microalga. The destination of carbon fixed was evaluated in terms of biomass and exopolyssaccharides production and as dissolved carbon, while nitrogen consumption was evaluated for protein and magnesium for chlorophyll production. B. braunii presented the highest CO2 fixation rate, followed by, S. platensis, D. tertiolecta and C. vulgaris (496.98, 318.16, 272.40, and 251.64 mg L-1 day-1, respectively). Nitrogen, potassium, magnesium and phosphorus (for D. tertiolecta calcium was analyzed instead of phosphorous) consumption rates (mg gX-1) were 49.35, 32.18, 2.85 and 314.4 for Chlorella vulgaris; 40.72, 15.02, 2.60 and 175.9 for B. braunii; 61.80, 24.09, 4.17 and 247.4 for S. platensis; and 26.05, 59.71, 58.45 and 375.46 for D. tertiolecta.
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